Kingswood's Richly Plaza was deserted over the weekend. Sharp-suited agents sat around polishing silent mobile phones, staring empty-eyed at computer terminals. Richly Plaza, a nondescript mall, has blossomed in the past year or so into a full-fledged real-estate market, boasting more than 40 agencies packed like sardines. In recent months, it teemed with prospective buyers and sellers elbowing...